METHOD AND APPARATUS FOR DIAGNOSING ROTARY MACHINE

PURPOSE:To diagnose whether a crack is generated or not in a revolving shaft, in accordance with a vibration waveform of every half period in 1 period portion of a detected vibration signal, by detecting the number of revolutions and the vibration of both end bearings of the rotor, when the rotor of the rotary machine is rotating. CONSTITUTION:Vibration of a rotor is diagnosed by detecting the number of revolutions in case when rotors 1-3 are rotating, and the vibration of bearings 41-46 of the rotors. A detectors 5 for the number of revolutions detects the number of revolutions of the rotor when the number of revolutions is raised or lowered. Also, a vibration detector 6 for detecting the journal vibration of the bearings 41-46 is provided. A detected vibration signal is dispersed within a range of 1 period, and is sent to the following subtractor 8. On the other hand, normal vibration in the beginning of a motion of the rotor is A/D-converted, and after that, is dispersed, and is stored in a storage device 9. A difference portion DELTAd=d1-d0 of a vibration signal d0 is derived by the subtractor 8, and is sent to an integrator 10. In case when abnormal vibration generated in the rotor is caused by a crack, crack vibration is diagnosed by a deciding device 11, from an integral value (e) or magnitude of the vibration waveform diffference portion DELTAd, and it is displayed on an indicator 12.